Nanomechanical Characterization of CdSe QD-Polymer Nanocomposites

Eddie McCumiskey Master’s Thesis Presentation 23 January 2008 Virginia Commonwealth University

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],http://www.solardirect.com/pv/consumer-ready/power-film.htm#fea Sony’s 3-mm thick TV www.sonystyle.com/oled

[object Object],[object Object],[object Object],[object Object],http://www.nn-labs.com/CdSe-orderform.htm Commercial CdSe Quantum Dots

[object Object],Mechanical Characterization

[object Object],[object Object],[object Object],[object Object],[object Object],Nanocomposite Mechanical Properties

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],*D. Lee et al., Phys. Rev. Lett. 98 .2 (2007)

[object Object],[object Object],[object Object],[object Object],[object Object]

QDs in a polymer matrix Conceptual Design of Experiment Example from the literature: organic solar cell made with blended CdSe nanoparticles and OC 1 C 10 -PPV* *Figure from: B. Sun, E. Marx, and N. C. Greenham, “Photovoltaic Devices Using Blends of Branched CdSe Nanoparticles and Conjugated Polymers.” Nano Lett . 3 .7 (2003) , pp . 691-963 . blended nanoparticle-polymer thin film Nanoindenter tip Characterizing the Mechanical Properties of Nanocomposite Films glass substrate Applied Load

I. Prepare QD-Polymer Solutions II. Deposit Films onto Glass III. Characterize Film Uniformity IV. Mechanical Characterization Nanoindentation TEM AFM Stirring Sonicating Spin-coating

[object Object],[object Object],[object Object],[object Object],[object Object],CdSe ODA Ligands 5.6 nm CdSe QDs Source: http://www.nn-labs.com/CdSe-orderform.htm

[object Object],[object Object],[object Object],MEH-PPV Structure Dry MEH-PPV *p oly[2- m ethoxy-5-2(2΄- e thyl h exyloxy- p henylene v inylene)] Source: http://www.adsdyes.com/products/pdf/homopolymers/ADS200RE_DATA.pdf

[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],+  MEH-PPV in toluene QDs in toluene MEH-PPV + QDs in toluene

[object Object],[object Object],[object Object],[object Object],A. Sonicate C. Deposit via Spin-Coating D. Anneal Filtering B.

[object Object],[object Object],Unfiltered Filtered Aggregation 20 μ m 200 μ m 200 μ m

[object Object],[object Object],[object Object],* N. C. Greenham, X. Peng, and A. P. Alivisatos, “Charge Transport in Conjugated-Polymer/ Semiconductor-Nanocrystal Composites Studied by Photoluminescence Quenching and Photoconductivity.” Phys Rev. B 54 .24 (1996 ), pp. 17628-17637. ligand

[object Object],[object Object],[object Object],[object Object],[object Object],QDs w/ Ligands QDs w/o Ligands LIGAND  Need to remove the ligands

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],* Modified method of Sun et al. ** suggested by Dr. David Goorskey ** B. Sun, E. Marx, and N. C. Greenham, “Photovoltaic Devices Using Blends of Branched CdSe Nanoparticles and Conjugated Polymers.” Nano Lett . 3 .7 (2003) , pp . 691-963 . *** W. U. Huynh, J. J. Dittmer, W. C. Libby, G. L. Whitting, and P. Alivisatos, “Controlling the Morphology of Nanocrystal-Polymer Composites for Solar Cells.” Adv. Funct. Mater. 13 .1 (2003) , pp. 73-79 . 2X Centrifuge

Ligand removed Ligand attached Unfiltered Filtered ,[object Object],[object Object],[object Object]

[object Object],* Vol% estimated using densities of 1 g/cm 3 for MEH-PPV* (Mirzov 2004) and 5.664 g/cm 3 for CdSe. ** O.Mirzov et al. “Direct Exciton Quenching in Single Molecules of MEH-PPV at 77 K.” Chem. Phys. Lett. 386 .4-6 (2004), pp. 286-290. *** S. Adachi, Handbook on Physical Properties of Semiconductors . Volume 3: “II-VI Compounds.” Springer-Verlag (2004). wt% QDs vol% QDs* 0% 0% 50% 15.0% 75% 34.6% 90% 61.4% 95% 77.0% 100% 100%

[object Object],[object Object],Veeco Multimode AFM LASER alignment Piezo tube scanner sample 10µm

wt% QDs: 100% 0% 50% 75% 90% 95% R a = 3.4 R a = 20.3 R a = 21.0 R a = 5.7 R a = 11.7 R a = 2.4 R a  Average Roughness (nm) 5 μm 5 μm

[object Object],[object Object],[object Object],[object Object],[object Object],Jeol 2010F TEM TEM grid Drop-casting

QDs in toluene (as-received) 90 wt% QDs in MEH-PPV 50 wt% QDs in MEH-PPV 3-D Architecture No QDs Noise from amorphous polymer ~5-6 nm QD 20 nm 20 nm 20 nm 5 nm 5 nm 5 nm

Load, P Displacement, h specimen Play h indenter tip hold segment loading segment unloading segment h f h max h c a h c hardness stiffness elastic modulus (reduced) cross-sectional area

[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],*A. C. Fischer-Cripps, Nanoindentaion . Springer Mechanical Engineering Series. New York (2002).

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],*Briscoe 1998 **Yang 2004 Load, P Displacement, h “ Nose” long hold

Indenter Tip Geometry -Images from: A. C. Fischer-Cripps, Nanoindentaion . Springer Mech. Engineering Series (2002). *Oliver, W. C. and G. M. Pharr. J. Mater. Res. 7 .6 (1992), pp. 1564-1583. θ = 65.3º Berkovich Indenter Tip <Rounded tip> Ideally: In actuality: Rounded at end h c

[object Object],[object Object],Overlapping Load-Displacement Curves Determine Area Function from Measured E r ’s scattered under 20 nm Check area function E r = 69.72 ± 3.26 GPA H = 8.52 ± 0.75 GPA

Nanoindenter Setup: Hysitron Triboindenter

Determining the Film Thickness ,[object Object],92 nm 224 nm

Film Thicknesses 11.35 6.98 4.48 17.11 11.67 19.33 Standard Deviation (nm) 131.36 156.42 85.15 162.62 85.61 201.62 Film Thickness (nm) 100% 95% 90% 75% 50% 0% wt% QDs

Nanoindentation Parameters Load-Control Test Cycle ,[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],Reduced Modulus (GPa) Contact Depth (nm)

Modulus vs. QD Loading ,[object Object],[object Object],Reduced Modulus (GPa) Wt% QDs in MEH-PPV Vol% QDs in MEH-PPV

Hardness vs. QD Loading ,[object Object],[object Object],Hardness (GPa) Wt% QDs in MEH-PPV Vol% QDs in MEH-PPV

Sample 0 wt% QDs (pure MEH-PPV) 100 μ N/s 10 μ N/s 1 μ N/s 1 μ N/s

Sample 0 wt% QDs (pure MEH-PPV) 100 µN/s 1 µN/s

Creep During the Hold Segment for Different Loading Rates 0 wt% QDs Time (s) Creep (nm)

0 wt% 50 wt% 75 wt% 95 wt% 100 wt% 90 wt% Creep During the Hold Segment for Different QD Loading

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[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Agilent PicoPlus System User’s Manual v1.2, “Aligning the Photodiode Detector.” pp . 1-18 Used with permission from http://barrett-group.mcgill.ca/yager/art.html http://www.nanoscience.com/products/AFM_tips.html

Nanomechanical Characterization of CdSe QD-Polymer Nanocomposites

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Nanomechanical Characterization of CdSe QD-Polymer Nanocomposites